Oropharyngeal candidiasis (OPC, thrush) is an opportunistic infection associated with T cell immunodeficiency, caused mainly by the commensal yeast Candida albicans. This organism also causes disseminated candidiasis, which is the 4th most common cause of hospital-acquired infections and has a 40% mortality rate. There are currently no vaccines available to any Candida species, or any other fungal organisms.
OPC is common in HIV/AIDS, chemotherapy, infants and the elderly, and certain congenital immunodeficiency diseases. The sensitivity of HIV patients to OPC implicates CD4+ T cells in immunity to this fungus. There are 3 subtypes of CD4+ T cells: Th1, Th2 and Th17, characterized by production of the cytokines IFNγ, IL-4 and IL-17A/IL-17F, respectively. Th17 cells are maintained by IL-23, and IL-17A/F signal through a receptor known as IL-17RA. It was previously reported that IL-17RA-/- and IL-23-/- mice are highly susceptible to OPC, whereas WT mice are resistant (Conti et al., J. Exp. Med 206(2):299-311, 2009).
IL-17 mediates immunity to OPC in large part by inducing expression of three CXC chemokines, CXCL1, CXCL2 and CXCL5, which help to recruit neutrophils and other myeloid cells to the oral cavity, where they facilitate clearance of the infection.